This invention relates to a display device in which driving time is controlled by a change of the ambient temperature.
A display element, for example, liquid crystal display device has a slow response at a low ambient temperature, and has a fast response at a higher ambient temperature. Therefore, a necessary driving voltage for operating said display element is changed according to the ambient temperature as indicated in FIG. 1 which illustrates the characteristics of temperature - driving voltage. Accordingly a minimum driving voltage for driving a display element becomes higher at a lower temperature, a on the contrary said minimum driving voltage for driving display element becomes lower at a higher temperature. A high driving voltage is necessary for operating the display element from the lower temperature to the higher temperature.
However, in case of driving the display element in a multiple system, the phenomenon of cross talk occurs at the higher driving voltage whereby it is necessary to develop and use the special display element for the multiplex system, and therefore the upper limit of the driving voltage is restricted.
Accordingly, there is a mutual relation as indicated by the curved line II in FIG. 1 between the maximum driving voltage and temperature of the display element whereby the cross-talk is more than a predetermined level.
When the driving voltage for the display element is set to e V in FIG. 1, the temperature range of display with good contrast and having no cross-talk is set between TIC.degree. and TIIC.degree.. Namely the good contrast is not obtained at less than TIC.degree., the cross-talk occurs above TIIC.degree..
The curved line I and II in FIG. 1 are changed by the driving time of the display element namely the duty ratio or duty cycle of the driving pulse. For a large duty ratio, the curved lines a and b are moved downward, and on the contrary for a small duty ratio, said curved lines a and b are moved upward. Therefore, setting a large duty ratio of the driving pulse in a constant driving voltage causes the minimum and maximum temperature at become lower, on the contrary, setting a small duty ratio causes said minimum and maximum temperature to become higher.